Where to find lots of nettles that preferably aren't covered in dog piss?

Very much not the northside, but at the junction of The Oaks and Hazel Hill in Maryborough Ridge on the southside, there is an elevated hedgerow. There are a huge amount of nettles growing throughout it. None touch the ground so I say you’re good when it comes to dogs. Still, probably best to make sure they aren’t sprayed with anything/touched by anyone

It's too late in the season for picking, I think.

It's off season for eating nettles, this is nettle season in america where the spring is later, or maybe up in the austrian alps somewhere, but not Cork down at sea-level. They are woody and tough in Ireland now, you need the young fresh growth. Next year, get them the same time of year as wild garlic… Best place to get them is an elderly neighbours' garden, in return for giving them a hand with weeding. ;)